Electron discharge device



y 3, 1948. P. J. CADE ELECTRON DISCHARGE DEVI-CE Filed Feb. 22, 1945 jNVENTOR. Pmzz mzm Patented July 13, 1948 2,444,915 :ELEcmcNmscuaneuDEYwE 'Apniiamh nitrite 22. 1945., serial. n a's gz The present invention relates as electron discharge "devices and more i particularly to such devices part of whose evacuated'envelo'peis made of metal and serves as an electrode.

It is one of the main objects of the present invention to provide an electron discharge *de'vice "which has'a minimum of parts andwh'icjh is "nevertheless 'very effective and reliable in per- "formancej Other-objects are to provideaphototube which has a minimum overall size but a maximum area of conductive and emitting material for a given window area; to provide a phototube which, due to its hemispherical construction, makes maximum use of the light impinging thereon; to provide an electron discharge tube of this type which has a long leakage path inside and outside between cathode and anode or parts conductively connected thereto, which in the case of a phototube results in a low dark current; to provide an electron discharge device whose construction inherently provides a shield for its electrically sensitive components; and to provide an electron discharge tube with moistureproof terminals which can be used even for work under water.

While the construction according to the present invention lends itself especially well for phototubes, it is understood that some of its features are applicable to other types of electron discharge devices.

These and other objects and aspects of the invention will be apparent from the following description of a specific embodiment of the invention which illustrates its general character. The description refers to a drawing in which Fig. 1 is a front elevation of a phototube according to the invention, with part of the window broken away;

Fig. 2 is a longitudinal cross section through a phototube according to Fig. 1;

Fig. 3 is a cross section on line 3-3 of Fig. 2; and

Fig. 4 is a cross section on line 44 of Fig. 2.

In the figures, II] is a hollow, or cup-shaped, in the present instance hemispherical, cathode portion made of a metal which has a coefficient of thermal expansion approximating that of glass or other material used for the insulating or transparent plate to be described below. Such metal is available for example in the alloy known under the trade name Kovar.

The cathode cup has a central opening II. The edge Id of this opening as well as the edge l5 of the mouth of the cathode cup are sharpened in order to provide a better seal. The mouth of the cathode cup' iscovered-with '=a' "window 'or' cqverplate 210. mace-er suitable -gla'ss un other liinsulating; and transparent materi'al. '-'-'1his wind'o'w is sealed to edge 15 by "conventional means, for examplehi-ghfrequency*induction 'apparatus.

During manufacture the plate 20 may be providedwith a tube for evacuating the vessel, as "indicatedbyseaI-ofi-Zl of Fig.--2-.- I

Fused to edge I fi' is asea'l 30 of -i-nsulating material, which may be the same as that of window 20. Through the center of seal 30 leads a pin 3| made of material similar to that of cathode cup Ill. The seal 30 is provided with inner and outer leakage sleeves indicated at 32, 33, respectively.

Suitably fastened, for example welded, to the inner end of pin 3| is ametallic anode body 40 which is drawn over the outside of sleeve 32 toward the supporting portion of seal 30. Suitably fastened, for example welded, to cup Ill is a tubular cathode connection and anode shield 50.

The cathode I0 is on the inside covered with a sensitive coating of suitable composition. The inside of the window may be covered with a transparent conductive and sensitized coating, to add to the photoelectric current.

The outer end of pin 31 and the sleeve 50 may be plugged into a concentrical receptacle of known type; if sleeve 50 is soldered to a socket of sealed design a waterproof connection is provided which permits immersion of the tube in water.

The operation of a phototube of this type is as follows.

Light is admitted through window 20, and the electrons released from the coating of cathode H) are collected at anode 40. Due to the hemispherical construction of the cathode, a maximum of the light flux entering through the window is utilized, the light being incident upon all parts of the cathode. The cathode cup, the conductive coating of window 20 if such is provided, and cathode connection sleeve 50 provide a complete shield for the anode assembly 3|, 40. Anode tube 40 protects sleeve 32 against accumulation thereon of conductive material, and sleeves 32 and 33, extending freely around conductor 3|, therefore constitute a very effective extension of the leakage paths between anode and cathode.

It will be evident that, since the cathode is part of the evacuated housing and borders directly on the window without any light obstructing supporting elements, a tube according to the invention necessarily has the smallest possible overall size for the given area of the window; in other words, the outer contour of the tube is 10 cover plate of insulating material sealed to the 1. A phototube comprising a hollofisubstantially hemispherical cathodehaving a substan tially centrally located opening opposite mouth, a substantially fiat transparentvcoverr. plate sealed to the rim of said cathode, an anode structure including a connector rod and a tube like member fastened to the tip of and extended ing substantially coaxially over said rod, an in- .sulatlng seal in said-opening fastening said rod to and leading it through said.,cathode,. said seal having a sleeve extending between said rod and said member, and a connector sleeve fastened .to said cathode substantiallyconcentrical to said rod;

p 2.. An electron discharge device Icom prising a substantially hemispherical electrode member having an opening in addition toits mouth, a

4 cover plate of insulating material sealed to the rim of said electrode member, a second electrode member including a stem and a tubular member around said stem, and an insulating seal in said opening fastening said stem to, and leading it through said first electrode member, said seal having a sleeve extending between said stem and said; tubular member,- I a 21.: 3. An electron ;discliarge,- device, comprising a substantially hemispherical electrode member, a

rim of saidelectrode member thus completing *a vessel which can be evacuated, a second rod- A like electrode member leading through and being insulated.fromsaid'first electrode member and ;forminga,connector pin, and a connector sleeve fastened to said first electrode member substantially coaxiallywith said pin.

, PHILLIP J. CADE.

I REFERENCES CITED The following.referencesare of record in the file-ofthispatentgp, I

UNI'I ED' STATES PATENTS Number Name Date f7 55,840 Bose Mar. 29,1904 2,306,376; Beuchon, Dec' v29, 1942 2,351,028 fFeai-on June 13, 1944 

